In a WCDMA system, the radio network controller (RNC) controls the data rate of uplink packet data transmission for a multiplicity of mobile stations (MS). The radio network controller scheduling of the uplink data rate can be combined with base station (BTS) scheduling in order to achieve better radio link efficiency and therefore higher system capacity. One example of this combination of the RNC and BTS packet scheduling is the so-called Enhanced Dedicated Channel (EUDCH). We refer here 3GPP TR 25.896 V1.2.1 (2004-01), Technical Report of 3GPP (3rd Generation Partnership Project).
In addition to packet scheduling capability at a base station, EUDCH considers a base station to have ARQ (automatic retransmission) capability in order to request retransmission of an erroneous data packet directly to the mobile station without the involvement of the radio network controller. Generally, BTS ARQ is much faster than RNC ARQ, hence the former outperforms the latter in terms of its required delay for retransmission.
When a mobile station has multiple uplink data flows, it is possible to use a different scheduling method for the different data flow depending on the requirement of the flow. For example, if the BTS scheduling is optimized for mainly a best-effort service while a voice call service can be better controlled by the RNC scheduling, the mobile station is able to transmit multiple data flows using appropriate scheduling mode to meet the requirement of each data flow.
FIG. 1 gives an illustration of a system with the BTS/RNC scheduling and ARQ. Three types of mobile stations (MS1 to MS3) 101 to 103 in a cell are connected to base station (BTS) 104 which is controlled by radio network controller (RNC) 105. Two mobile stations (MS2, MS3) 102, 103, which are denoted as “BtsSch,” are BTS scheduled mobile stations while two mobile stations (MS1, MS3) 101, 103, which are denoted as “RncSch,” are scheduled by radio network controller 105. Note that MS3 103 has two data flows and each flow has a different scheduling mode, i.e., BtsSch and RncSch. In other words, MS3 103 has two uplink data flows while each of MS1 101 and MS2 102 has one uplink data flow. Hence the data rate of MS2 102 and the data rate of the first flow of MS3 103 are controlled by base station 104 while radio network controller 105 controls the data rate of MS1 101 and the data rate of the second flow of MS3 103. Similarly, the retransmission of MS2 102 and the retransmission of the first flow of MS3 103 are requested by the base station while the radio network controller controls the retransmission of MS1 101 and the retransmission of the second flow of MS3 103. It is important to note that MS1 101 is connected to both base stations 104, 104A at the same time and radio network controller 105 combines received data packets from two base stations 104, 104A.
When a mobile station transmits two data packet flows using both the BTS and RNC scheduling simultaneously, assuming the user is making a voice call while sending a multimedia message, the transmission power of two data flows should be appropriately controlled. In the example of the aforementioned EUDCH, the transmission power of two data flows, denoted by DCH (dedicated channel) and EUDCH (enhanced dedicated channel), can be conventionally controlled in the following manner:Pcch(t)=Pcch(t−1)+Δcch(t)Pdch(t)=PODCH Pcch(t)Peudch(t)=POEUDCH Pcch(t)  (1)where PODCH and Pdck(t) are the transmission power offset and transmission power at time t of DCH (RNC scheduled data flow) while POEUDCH and Peudch(t) are those of EUDCH (BTS scheduled data flow). The power offsets of DCH and EUDCH are controlled in a semi-static manner by the radio network controller while the transmission power of pilot signal Pcch(t) is controlled by both inner and outer loop control. More specifically, Δcch(t) composes of inner and outer loop adjustment factors. We refer both adjustment algorithms included in 3GPP TS 25.214 V5.6.0 (2003-09), Technical Report of 3GPP (3rd Generation Partnership Project).
The literatures cited in this description will be listed below:
[1] 3GPP TR 25.896 V1.2.1 (2004-01) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Feasibility Study for Enhanced Uplink for UTRA FDD; (Release 6)
[2] 3GPP TS 25.214 V5.6.0 (2003-09) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical layer procedures (FDD) (Release 5)